Chapter I: Part 1

UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY

Volume 18, No. 6, pp. 505-545, 7 figs., 4 pls.

December 2, 1969

The Systematics of the Frogs of the _Hyla rubra_ Group in Middle America

BY

JUAN R. LEON

University of Kansas Lawrence 1969

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: Frank B. Cross, Philip S. Humphrey, Robert M. Mengel.

Volume 18, No. 6, pp. 505-545, 7 figs., 4 pls. Published December 2, 1969

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY ROBERT R. (BOB) SANDERS, STATE PRINTER TOPEKA, KANSAS 1969

The Systematics of the Frogs of the _Hyla rubra_ Group in Middle America

BY

JUAN R. LEON

CONTENTS

PAGE

INTRODUCTION 508
Acknowledgments 508
Materials and Methods 509

THE HYLA RUBRA GROUP 509
Key to Species and Subspecies 510
Key to Known Tadpoles 511

ACCOUNTS OF SPECIES AND SUBSPECIES 511
_Hyla boulengeri_ (Cope) 511
_Hyla foliamorta_ Fouquette 520
_Hyla rubra_ Laurenti 524
_Hyla elaeochroa_ Cope 525
_Hyla staufferi_ Cope 532
_Hyla staufferi staufferi_ Cope 537
_Hyla staufferi altae_ Dunn 540

EVOLUTIONARY HISTORY 540

LITERATURE CITED 543

INTRODUCTION

The tree frogs of the _Hyla rubra_ group are abundant and form a conspicuous element of the Neotropical frog fauna. Representatives of the group occur from lowland Mexico to Argentina; the greatest diversity is reached in the lowlands of southeastern Brazil (Cochran, 1955). The group apparently originated in South America; the endemic Central American species evolved from stocks that invaded Middle America after the closure of the Colombian Portal in the late Pliocene.

Dunn (1933) partially defined the _rubra_ group as it occurs in Central America. Cope (1865, 1876, 1887), Brocchi (1881), Boulenger (1882), Guenther (1901), Noble (1918), Kellogg (1932), Dunn and Emlen (1932), Stuart (1935), and Gaige (1936) dealt with the Middle American species now considered to make up the _rubra_ group. More recently, Taylor (1952, 1958), Fouquette (1958), Starrett (1960), and Duellman (1960, 1963, 1966a) studied aspects of the taxonomy and biology of the species of this group. The five species of the _rubra_ group in Central America have received ten different names. One species, _Hyla staufferi_, has received five names (two subspecies are recognized herein). _Hyla boulengeri_ was named in the genus _Scytopis_, but the type species of _Scytopis_ is a member of the genus _Phrynohyas_ Fitzinger, 1843 (Duellman, 1956.)

Little has been published concerning the ecology, life history, osteology, and mating calls of the Middle American species of this group. The purpose of the present report is to describe the species occurring in Middle America and to comment on their distributions, ecology, cranial osteology, and mating calls, and in so doing provide evidence for the evolutionary history of the species inhabiting Middle America.

Acknowledgments

For permission to examine specimens in their care, I am grateful to Drs. Richard G. Zweifel, American Museum of Natural History (AMNH); Robert F. Inger, Field Museum of Natural History (FMNH); Ernest E. Williams, Museum of Comparative Zoology (MCZ); Hobart M. Smith, University of Illinois Museum of Natural History (UIMNH); Charles F. Walker, University of Michigan Museum of Zoology (UMMZ); Jay M. Savage, University of Southern California (USC); James A. Peters, United States National Museum (USNM); Richard J. Baldauf, Texas Cooperative Wildlife Collection (TCWC); and W. Frank Blair, Texas Natural History Collection (TNHC). KU refers to specimens in the Museum of Natural History, University of Kansas. For the loan of tape-recordings of mating calls I thank Drs. W. Frank Blair, University of Texas, and Richard G. Zweifel, American Museum of Natural History.

I am indebted to the Ford Foundation-Universidad de Oriente (Venezuela) Science Project for a scholarship which enabled me to study for two years at The University of Kansas, foster institution of the project. I have benefited by being able to work in the Museum of Natural History at The University of Kansas and I am grateful to Dr. E. Raymond Hall, Director, for providing space and equipment.

I gratefully acknowledge the assistance and advice of Dr. William E. Duellman, who suggested and directed this work, made available specimens under his care and gave much of his time in reading the manuscript and suggesting improvements. I am grateful to Dr. Frank B. Cross who critically read the manuscript and made many editorial suggestions. I am indebted to Linda Trueb for assistance with the osteological aspects of this study; she helped to clarify many confusing points. I am grateful to Charles W. Myers for making available his field notes on these frogs in Panama, to Arthur C. Echternacht for reading part of the manuscript, and to John D. Lynch for many suggestions and helpful criticisms. The illustrations were executed by David M. Dennis.

Materials and Methods

For the purposes of the present study I examined 1383 preserved specimens, 50 skeletons, and 9 lots of tadpoles. External characteristics used in the analysis of variation are those currently employed in the study of anuran systematics. Twelve measurements and six proportions were taken in the manner described by Duellman (1956). Only the most important references are given in the synonymies, except those of the two subspecies of _Hyla staufferi,_ which are more nearly complete. The taxonomic history of each frog is discussed under _Remarks_ in each account. The cranial osteology was studied by using skeletons and cleared and stained specimens of all species. Developmental stages of tadpoles were determined from Gosner's (1960) table. Personal field work in Central America in the summer of 1966 provided an opportunity to make observations on the ecology, calling sites, and color in life; these data were supplemented by field notes from, and discussions with, Dr. William E. Duellman and Charles W. Myers.

The mating calls of the frogs were recorded in the field on Magnemite and Uher Tape Recorders by Dr. Duellman in the course of his work on the hylid frogs of Middle America--supported by grants from the National Science Foundation (G-9827 and GB-1441). These recordings, plus those borrowed from other institutions, provided 50 tapes for analysis of the mating calls. The calls were analyzed on a Vibralyzer (Kay Electric Company).

THE HYLA RUBRA GROUP

_Definition._--The species forming the group are small to moderate-sized tree frogs (maximum snout-vent length of males of various species 20-49 mm.), distinguished from other groups in the genus _Hyla_ as follows: Brown, grayish brown, or yellowish tan above; thighs plain, marbled with dark brown, or having vertical bands; vocal sac single, median, subgular; snout flat, protruding, rounded or pointed; webbing between fingers reduced or absent; web between first and second toes reduced to fringe on second toe, rest of toes about half webbed; tarsal fold reduced or absent; shanks robust; inner metatarsal tubercle larger than outer; prevomerine teeth on transverse ridges between small to large sized choanae; skull generally longer than wide; nasals large (length more than 40 per cent total length of skull) and having pointed maxillary processes; maxillary bearing small ventromedial palatine process; quadratojugal slender, always joined to maxillary by bony suture; auditory region of prooetic slender and short; delicate spatulate columella ventral to crista parotica, broad basally, compressed anterolaterally, slightly rounded distally; anterior arm of squamosal extending about half distance to maxillary; sphenethmoid wider than long; frontoparietal fontanelle present or absent; prevomerine, premaxillary, and maxillary teeth present; prevomer with two lateral processes forming incomplete bony margin to internal nares; tadpoles having pointed xiphicercal tail, snout short, rounded; 2/3 tooth rows; dorsal fin deeper than ventral fin; sinistral spiracle; short dextral anal tube not reaching edge of ventral fin; mating calls consisting of single long note or series of short notes.

_Composition._--This group contains about 24 currently recognized species, most of which occur in Brazil. Only five species--_boulengeri,_ _elaeochroa_, _foliamorta_, _rubra_, and _staufferi_ with two subspecies--occur in Central America. _Hyla boulengeri_ and _rubra_ are widespread in South America, and _foliamorta_ occurs in Colombia, whereas the other species are known only from Middle America.

_Distribution._--The species of the _Hyla rubra_ group range from the lowlands of northern Argentina and Bolivia to southern Tamaulipas and Guerrero, Mexico.

_Comments._--In Central America two subgroups of species can be recognized. _Hyla boulengeri_ and _H. foliamorta_ are distinctive in the large size of adults (snout-vent lengths 41-49 mm.); both have prominent bars on the thighs, a well-defined interorbital triangular mark, blotches or spots dorsally, and large choanae. _Hyla elaeochroa,_ _H. rubra,_ and _H. staufferi_ are smaller (snout-vent lengths 29-40 mm.); they have the thighs weakly barred or vermiculate anteriorly and posteriorly or unmarked, an ill-defined interorbital triangular mark, linear markings dorsally, and small choanae.

Key to Species and Subspecies

1. Larger frogs (males to 49 mm. snout-vent length); thighs
strongly barred; supratympanic fold black; dorsum blotched or
spotted 2

Smaller frogs (males to 40 mm. snout-vent length); thighs weakly
barred or plain; supratympanic fold pale brown; dorsum usually
having linear pattern 3

2. Dorsum tuberculate; snout subacuminate; vocal sac flecked with
brown; tarsal fold rudimentary; web absent between fingers; black
spots absent in scapular region _H. boulengeri_

Dorsum smooth; snout pointed; vocal sac dark gray; tarsal fold
absent; trace of web between fingers; two or more elongate dark
spots in scapular region _H. foliamorta_

3. Snout-vent length more than 30 mm.; tympanum 2/3 to 3/4 diameter
of eye; prevomerine elevations about size of choanae 4

Snout-vent length less than 30 mm.; tympanum less than 1/2 diameter
of eye; prevomerine elevations smaller than choanae 5

4. Thighs mottled posteriorly; discs on fingers about 1/2 size of
tympanum; faint dark line from nostril to eye _H. rubra_

Thighs faintly barred or plain posteriorly; discs on fingers
about size of tympanum; distinct dark line from nostril to eye
_H. elaeochroa_

5. Dorsum brown with irregular dorsolateral stripes and
interrupted paravertebral stripes; two transverse bars on shanks;
interorbital bar present _H. staufferi staufferi_

Dorsum gray with complete dorsolateral and paravertebral stripes;
longitudinal stripe on shank; interorbital bar absent
_H. staufferi altae_

Key to Known Tadpoles

1. Entire lower beak black; beaks moderate-sized, serrate; dorsal
fin high, extending to middle of back 2

No more than half of lower beak black; beaks small, finely serrate;
dorsal fin lower, barely extending onto body 3

2. Papillae present only laterally _H. boulengeri_
Papillae present laterally and ventrally _H. foliamorta_

3. Distinct brown stripe from nostril to eye; two stripes below
eye, _H. elaeochroa_

Faint stripe from nostril to eye; no stripe below eye
_H. staufferi_

ACCOUNTS OF SPECIES AND SUBSPECIES

_Hyla boulengeri_ (Cope)

_Scytopis boulengeri_ Cope, Bull. U.S. Natl. Mus., 32:12, December
1, 1887 [Holotype.--USNM 13974, from "Nicaragua"; J. A. McNiel,
collector].

_Hyla boulengeri:_ Guenther, Biologia Centrali-Americana, Reptilia
and Batrachia, p. 267, June 1901. Noble, Bull. Amer. Mus. Nat.
Hist, 38:339, June 1918. Taylor, Univ. Kansas Sci. Bull., 35:856,
July 1, 1952.

_Diagnosis._--Size large (Male to 49 mm., Female to 53 mm.); skull as long as wide; frontoparietal fontanelle present; snout subacuminate; canthus not pronounced; choanae large; tongue cordiform, slightly longer than broad; interorbital triangle tubercular; skin on dorsum tuberculate; tarsal fold reduced or absent; thighs, shanks, and tarsi boldly barred with dark brown and pale yellow-green in life.

_Description._--Head flattened, longer than wide; snout projecting beyond lower lip; loreal region oblique; canthus not pronounced; length of eye less than interorbital distance; tympanum large, about 70 per cent of diameter of eye; interorbital triangle distinct; arms short; fingers lacking web; palmar tubercle tripartite; subarticular tubercles distinct; long tubercle on base of first finger; discs truncate; legs long; tarsal fold reduced or absent; inner metatarsal tubercle rounded, larger than outer, both elevated; subarticular tubercles distinct; one phalanx free of web on second, third, and fifth toes, three free on fourth toe (Fig. 1A and B); skin tuberculate on dorsum, less so on flanks; skin of belly granular, that on chest and throat weakly granular; tongue cordiform, longer than wide, free and notched behind; vocal slits large, lateral to tongue.

In life, dorsum tan or brown with dark spots on snout, head, and scapular region; interorbital triangle and blotch posteriorly on dorsum dark brown; flanks pale green; groin pale green or orange, mottled with dark brown; thighs tan or brown above with dark transverse bars on anterior and posterior surfaces; spaces between bars green or orange; inner surfaces of shanks and outer surfaces of tarsi brown and orange; foot brown above; forelimbs brown and pale green above, weakly barred; belly creamy white with scattered brown spots; vocal sac creamy white flecked with brown; lower jaw brown with white spots on lips (Pl. 1A).

In preservative, head and dorsum dark brown with triangular spot between eyes; dark spots on head and scapular region and dark brown blotch posteriorly on dorsum; flanks creamy white with brown spots; groin creamy white mottled with dark brown; thighs brown above with dark brown transverse bars on anterior and posterior surfaces; inner surfaces of shanks and outer surfaces of tarsi barred with pale brown; dorsal surface of foot mottled brown and creamy white; ventral surface of foot and toes pale brown; forelimbs faintly barred with pale brown; belly white with a few pale brown spots; vocal sac flecked with pale brown; lower jaw marked with small white spots on lips.

_Variation._--Geographic variation is evident in the snout-vent length, tibia length, and foot length, all in relation to snout-vent length, and the relative size of the tympanum to the eye (Table 1). The largest specimens are from the humid Pacific lowlands of Costa Rica; individuals from the Caribbean lowlands of Costa Rica, Canal Zone, and South America are smaller. A general trend for increase in size extends from South America to the Pacific lowlands of Costa Rica.

Most variation in color does not seem to be correlated with geography; color variation is nearly as great within a given population as between separated populations. However, most specimens from Rincon de Osa, Puntarenas Province, Costa Rica, are dusky brown, but a few are darker. In comparison with specimens from the Caribbean lowlands of Central America, specimens from the Pacific slopes in Costa Rica have a darker interorbital triangle. In some specimens from the latter area rugosities are present on the borders of the interorbital triangle, on the snout, on the upper eyelid, and on the heel. Specimens from the Caribbean lowlands are less tuberculate, and most individuals from there lack rugosities on the tarsus. Living individuals from Puerto Viejo, Heredia Province, Costa Rica, and from the Canal Zone, Panama, are brown above with a metallic green tint. Rugosities are present on the posterior edges of the forelimbs in some specimens from throughout the range. In most respects, specimens from the Canal Zone resemble those from the Caribbean lowlands of Costa Rica more than they resemble those from the Pacific lowlands of Costa Rica, but some individuals from the Canal Zone are less metallic above and have small white spots dorsally on the body, head, and limbs.

A moderate amount of color change from night to day has been noted. At night, a male from Puerto Viejo, Heredia Province, Costa Rica, was grayish tan above with slightly darker markings; the flanks were pale yellowish green. By day, the dorsum was brown with darker markings, and the throat was pale gray with white flecks; the rest of the venter was creamy white. The groin was pale green with black mottling; the anterior and posterior surfaces of the thighs and inner edges of the tarsi were greenish yellow with black bars.

TABLE 1.--Geographic Variation in Size and Proportions in Males of _Hyla boulengeri_. (Means in parentheses below observed ranges.)

=========================================================================
| | Snout-vent| Tibia | |
| | length | length/ |Tympanum/|Foot length/
Locality | N | (mm.) | snout-vent| eye | snout-vent
--------------------+----+-----------+-----------+---------+-------------
Costa Rica: Tilaran | 23 | 37.4-48.7 | 0.52-0.58 |0.62-0.76| 0.39-0.45
| | (43.8) | (0.55) | (0.71) | (0.42)
| | | | |
Costa Rica: Rincon | 10 | 41.4-46.1 | 0.54-0.60 |0.68-0.80| 0.40-0.45
de Osa | | (44.0) | (0.57) | (0.74) | (0.43)
| | | | |
Costa Rica: Alajuela| 13 | 35.6-43.1 | 0.55-0.60 |0.63-0.78| 0.41-0.46
Province | | (39.8) | (0.57) | (0.69) | (0.44)
| | | | |
Costa Rica: Puerto | 25 | 37.5-42.9 | 0.51-0.62 |0.63-0.79| 0.38-0.46
Viejo | | (41.6) | (0.55) | (0.71) | (0.43)
| | | | |
Costa Rica: Suretka | 9 | 38.7-42.0 | 0.56-0.58 |0.53-0.72| 0.35-0.45
| | (41.0) | (0.56) | (0.62) | (0.42)
| | | | |
Panama: Canal Zone | 16 | 36.7-42.9 | 0.52-0.58 |0.70-0.78| 0.40-0.44
| | (39.0) | (0.54) | (0.74) | (0.42)
| | | | |
Venezuela: Santome | 4 | 35.5-40.9 | 0.45-0.48 |0.63-0.67| 0.36-0.40
| | (38.5) | (0.46) | (0.65) | (0.38)

TABLE 2.--Comparison of Mating Calls in the _Hyla rubra_ Group. (Means in parentheses below observed ranges.)

============================================================================
| |Notes| | | | Major frequencies
| | per |Duration| Pulses|Fundamental| (cps)
| |call | of note| per | frequency |---------------------
Species | N |group| (sec.) | second| (cps) | Lower | Upper
---------------+---+----+---------+-------+-----------+---------+-----------
H. boulengeri | 8 | 1 | 0.24- | 80-120| 70-74 |1400-1820|2520-3182
| | | 0.47 | (101)| (71) | (1611) | (2840)
| | | (0.35) | | | |
| | | | | | |
H. foliamorta | 7 | 1 | 0.23- | 50-60 | 52-61 | 912-1026|2736-3477
| | | 1.86 | (51) | (56) | (918) | (3055)
| | | (0.69) | | | |
| | | | | | |
H. elaeochroa |15 | 2-95| 0.12- | 40-50 | 48-65 |1254-1586|2562-3477
| | (19)| 0.24 | (42) | (57) | (1499) | (2911)
| | | (0.17) | | | |
| | | | | | |
H. s. staufferi|18 | 2-77| 0.13- |100-130| 96-130 |1582-1872|1962-3744
| | (23)| 0.23 | (120) | (106) | (1743) | (3056)
| | | (0.18) | | | |
| | | | | | |
H. s. altae | 7 | 2-22| 0.14- |110-130| 104-117 |1853-2106|3379-4056
| | (11)| 0.18 | (120) | (112) | (2008) | (3775)
| | | (0.15) | | | |

_Cranial Osteology._--The skull of _Hyla boulengeri_ is as long as it is wide, and is flat; the premaxillary is small and bears 13 to 17 teeth (mean for 6 specimens, 14.9). The alary processes of the premaxillaries are widely separated, concave posteriorly, and vertical. Ventrally, the premaxillary is connected to the prevomer by bony tissues. The maxillary is slender and bears 70 to 91 teeth (mean for 6 specimens 78.1). The pars facialis of the maxillary is laterally convex and about four times as high as the pars dentalis.

The nasal is large (its length about 40 per cent of total length of skull), and pointed anteriorly and posteriorly in dorsal view. The nasals are separated anteromedially by the cartilaginous septum nasi. One or two protuberances are present on the midlateral concavity of the nasal. Posteriorly, the nasal overlaps the sphenethmoid and articulates with the palatine. Dorsally the sphenethmoid is large, pentagonal, and completely ossified. The frontoparietal is elongate, smooth, and bears a small supraorbital process on the anterior edge of the orbit. A keyhole-shaped frontoparietal fontanelle is present; the fontanelle is narrow anteriorly and wide posteriorly.

The bony part of the prooetic is separated dorsally from the squamosal by the cartilaginous crista parotica. The squamosal is small, its anterior arm slender and pointed. The posterior arm of the squamosal is pointed terminally and articulates with the prooetic medially.

The prevomer is large and elongate. Anteriorly the prevomer is connected to the maxillary-premaxillary articulation; posteriorly, the prevomer is separated from the sphenethmoid by cartilage. Each prevomer bears six to nine teeth. The palatine is present and edentate. The anterior end of the parasphenoid is broad (less pointed than in _Hyla foliamorta_). The pterygoid is slender and well developed.

_Natural History._--_Hyla boulengeri_ inhabits humid lowland tropical forests and breeds in temporary ponds. Clasping pairs and gravid females were observed at Puerto Viejo, Heredia Province, Costa Rica, on June 21, 1966. Males were calling from depressions in decaying logs and stumps, in forked stems, and from leaves of broad-leafed plants near the pond. Males were observed in late July and early August calling from _Calathea_ and _Heliconia_ leaves at the edge of a pond in the wet forest of the Osa Peninsula. William E. Duellman informed me that he collected calling males in January at El Real, Darien, and in March at Almirante, Bocas del Toro, Panama. Taylor (1952) found calling males in June at Turrialba, Cartago Province, Costa Rica, and Dunn (1931a) observed males calling in July, November, and December in Panama. Gravid females have been found from April to August. Breeding activities of _Hyla boulengeri_ always seem to be associated with temporary ponds; in Central America breeding apparently takes place throughout most of the year.

The mating call of _Hyla boulengeri_ consists of one short, moderately low-pitched note. Each note has a duration of 0.24 to 0.47 second and is repeated at intervals of one second to several minutes. The notes have 80 to 120 pulses per second, a fundamental frequency of about 70 cycles per second, and a dominant frequency of 2,840 cycles per second (Table 2, Pl. 3A).

The eggs are deposited in a mass in the water. No information is available concerning early development. Tadpoles in advanced stages of development were found in a temporary pond at Rincon de Osa, Puntarenas Province, Costa Rica. The pond was about 10 cm. deep, had a muddy bottom and lacked vegetation. Three recently metamorphosed young were found in mid-August, 1966, on grass at the edge of another temporary pond in the forest.

_Tadpoles_--Twelve tadpoles are available. These were collected at Rincon de Osa, Puntarenas Province, Costa Rica. The maximum size represented is 34.0 mm., total length (stage 42 of development).

A typical tadpole in stage 36 of development (KU 104295) has a body length of 12.0 mm., tail length of 20.0 mm., and total length of 32.0 mm. Other characters are as follows: depth of tail equal to length of body; body deeper than wide; distance between eye and nostril equal to that between nostril and tip of snout; mouth anteroventral, upper and lower lips bare; papillae present laterally; tooth rows 2/3; upper rows about equal in length; first upper row slightly, and second upper row widely, interrupted medially; lower rows about equal in length, shorter than upper rows; third lower row containing 5-10 large teeth; beak strong, serrate; spiracle nearer anus than eye; anal aperture not extending to border of ventral fin; caudal musculature slender posteriorly, extending to tip of pointed tail; dorsal fin extending to middle of body, slightly deeper than ventral fin; posterior three fourths of tail spotted; rest of tail and body gray-brown or transparent; hindlimbs flecked or spotted with brown (Table 3, Fig. 2A and 3A).

TABLE 3.--Sizes of Tadpoles of _Hyla boulengeri_ in Relation to Developmental Stages. (Means in parentheses below observed ranges; measurements in mm.)

=======================================================
Stage | N | Body length | Tail length | Total length
--------+---+-------------+-------------+--------------
30 | 1 | 11.0 | 22.2 | 33.2
| | | |
35 | 1 | 11.0 | 12.0 | 23.0
| | | |
36 | 3 | 9.5-12.0 | 20.0-21.5 | 31.0-32.0
| | (11.2) | (20.5) | (31.7)
| | | |
38 | 2 | 11.5 | 22.0 | 33.5
| | | |
42 | 2 | 10.5-13.0 | 21.0-22.0 | 32.5-34.0
| | (11.8) | (21.5) | (33.3)
| | | |
44 | 2 | 14.0-15.0 | 8.0-15.0 | 22.0-30.0
| | (14.5) | (12.5) | (26.0)
| | | |
46 | 1 | 15.0 | 15.0 |

A recently metamorphosed young has a snout-vent length of 15 mm.; the head is as long as wide, the eyes are prominent; the limbs are weakly barred; the skin is rugose above and granular below. The venter is immaculate; the dorsum and limbs are gray-brown in preservative (pale green in life). The interorbital space, supratympanic fold, and scapular region are darker than the rest of the body; the fingers lack webbing; the webbing on the foot is the same as in adults; small metatarsal tubercles are present, but the tarsal fold is absent.

_Remarks._--Cope (1887:12) described _Scytopis boulengeri_ from Nicaragua. Guenther (1901:267) placed _boulengeri_ in the genus _Hyla_, and stated that Cope possibly placed _boulengeri_ in the genus _Scytopis_ on the supposition that it had an accumulation of "sebaceous glands" above the tympanum. Noble (1918:339) redescribed _Hyla boulengeri_ on the basis of three specimens from Zelaya Province, Nicaragua, and noted that the glands were not prominent in any of the specimens. Duellman (1956:8) showed that _Scytopis hebes_ (generotype of _Scytopis_ by monotypy) is a Phrynohyas, and thus placed _Scytopis_ Cope, 1862, in the synonymy of _Phrynohyas_ Fitzinger, 1843.

Dunn and Emlen (1932:25) placed _Hyla lancasteri_ Barbour in the synonymy of _Hyla boulengeri_; the former was known solely from one juvenile. They made no qualifying statements, but probably they were impressed by the strongly barred thighs, a coloration known among Central American hylids at that time only in _Hyla boulengeri_ (Duellman, 1966a:271). Taylor (1952:856) followed Dunn and Emlen with reservation and noted some differences. Duellman (1966a:271) showed that the holotype of _lancasteri_ was a juvenile of a species subsequently named as _Hyla moraviaensis_ by Taylor (1952:865).

In Central America, _Hyla boulengeri_ can be confused only with _Hyla foliamorta;_ the latter is restricted to central and eastern Panama and northern Colombia. The snout of _foliamorta_ is more pointed and protruding, and the vocal sac is darker than in _boulengeri_; the groin of _foliamorta_ usually is creamy white, whereas _boulengeri_ usually has a dark spot. The skulls differ in that _boulengeri_ has a frontoparietal fontanelle, the prevomer is larger and elongate, anteriorly connected to the premaxillary, and posteriorly separated from the sphenethmoid by cartilage; _foliamorta_ lacks a fontanelle, the prevomer is smaller, anteriorly separated from the premaxillary by cartilage, but connected by a bony suture to the sphenethmoid. The mating call of _boulengeri_ differs by having shorter notes, twice as many pulses per second, a higher fundamental frequency, and more closely approximated major frequencies than does that of _foliamorta_.

_Hyla boulengeri_ need not be compared in detail with the other Central American members of the _Hyla rubra_ group, because all of them are smaller and have shorter snouts, smoother skin, and dissimilar color patterns.

_Distribution._--In Central America _Hyla boulengeri_ inhabits the forested lowlands in locally humid areas in Guanacaste Province, Costa Rica, and in the humid Golfo Dulce region of Costa Rica; it occurs on the Carribbean lowlands from central Nicaragua to South America, where it ranges to Guyana and Ecuador. The highest elevations where _H. boulengeri_ has been found are 620 meters at Turrialba, Cartago Province, and 700 meters at Tilaran, Guanacaste Province, Costa Rica (Fig. 4).

_Specimens Examined._--Costa Rica: _Alajuela_: 9 km N Ciudad Quesada, near La Florencia, USC 8059 (4); 18 km N Florencia, USC 2624; Laguna Monte Alegre, KU 64334; Las Playuelas, 11 km S Los Chiles, USC 7216, 7217 (2), 7219; 3 km NE Muelle del Arenal, USC 2644 (5). _Cartago_: Turrialba, KU 24741. _Guanacaste_: 7 km N Liberia, USC 8096 (2), 8138 (6); 13.6 km N Liberia, USC 8151, 8171 (2); 20.5 km S Liberia, USC 8205; Taboga, 20 km SE Las Canas, KU 102170, USC 7166; 4 km NE Tilaran, USC 8023; 6 km NE Tilaran, USC 523 (3), 6262, 7019. _Heredia_: Puerto Viejo, KU 64323-7 (skeletons), 104351-3 (skeletons), 64330-3, 103592-620; 1 km NE Puerto Viejo, UMMZ 126042; 1 km S Puerto Viejo, KU 84983-4 (skeletons), 86317-22, 87774 (skeleton); 4.2 km W Puerto Viejo, KU 64329, 64328 (skeleton). _Limon_: Mountain Cow Creek, near Banano, KU 37031, 41067 (skeleton); 3 km S Rio Tortuguero, AMNH 69057; Suretka, KU 36482-8, 36699. _Puntarenas_: 4.8 km S Bahia Rincon on NW side Rio Rincon, USC 705; Parrita, USC 6163; 4.5 km W Rincon de Osa, KU 102177-9, 104295-6 (tadpoles); 6 km SW Rincon de Osa, KU 102171-6; 4.4 km NW Villa Neilly, USC 8003; 10.5 km WNW Villa Neilly, KU 64321. _San Jose_: 21 km WSW San Isidro el General, KU 34104-6.

Panama: _Bocas del Toro_: 3.2 km W Almirante, KU 95978. _Canal Zone_: Barro Colorado Island, FMNH 13379; near Clayton Reservation, UIMNH 42000; 2.6 km SW Fort Kobbe, KU 95977; Miraflores Locks, AMNH 69764-5; Summit, AMNH 73445, KU 97777, 101540-9, 104350 (skeleton). _Colon_: Rio Gatuncillo, near Nuevo San Juan, KU 95976. _Darien_: El Real, KU 80451-3.

_Hyla foliamorta_ Fouquette

_Hyla foliamorta_ Fouquette, Herpetologica, 14:125, April 25,
1958 [Holotype.--TNHC 23109, 11 km. NW Miraflores Locks, Canal
Zone, Panama; M. J. Fouquette, Jr. collector].

_Diagnosis._--Size medium (Male to 43 mm., Female to 41 mm.); skull longer than wide; frontoparietal fontanelle absent; snout acuminate, projecting; interorbital triangle bordered by white lines; scapular region having two or more elongate spots; dorsum smooth; vocal sac dark gray; groin creamy white; traces of web between fingers.

_Description._--Head flattened, longer than wide; snout flat, pointed, protruding beyond lower lip; loreal region slightly concave; canthus moderately prominent; eyes smaller than interorbital space; tympanum distinct, 55 to 75 per cent of diameter of eye, smaller than internarial space; arms short; fingers having rudimentary webs; median palmar tubercle tripartite; inner palmar tubercle on base of first finger flat; subarticular tubercles distinct; discs of fingers smaller than diameter of tympanum; legs long; tarsal fold lacking; inner metatarsal tubercle larger than outer; one phalanx free on second, third, and fifth toes, two and one half phalanges free on fourth toe; narrow fringe continuing from web to discs of toes; discs of toes about the size of those on fingers; skin smooth on dorsum and flanks, that on belly and posterior part of thighs granular; tongue oval, longer than wide; vocal slits oblique, about one half length of tongue.

In life, dorsum pale tan to pale reddish brown with irregular reddish brown markings; small dark spots on head; distinct dark brown triangular mark between eyes, bordered by thin white lines; apex of triangle always directed backward; supratympanic fold with black edge; scapular region having two to five small, elongate black spots; belly creamy tan with small brown spots; vocal sac uniformly dark brown with scattered creamy tan flecks; upper jaw dark brown; limbs creamy white below with scattered brown spots; groin marked with small brown spots in some specimens; anterior and posterior surfaces of thighs yellow-orange with three distinct black blotches; two dark bands on upper surface of shanks; webbing of feet yellowish tan with brown mottlings (Pl. 1B).

In preservative, dorsum brown or gray with darker markings; interorbital triangle distinct, bordered by white lines; supratympanic fold with black edge; two or more small elongate black spots in scapular region; belly white with numerous brown flecks; edge of upper lip dark brown; vocal sac dark gray; undersides of limbs creamy white; groin creamy white with or without brown spots; anterior and posterior surfaces of thighs having three black blotches separated by creamy white spaces; shanks having two brown bands; webbing of feet mottled with brown.

_Variation._--Twenty-eight breeding males from the area between Chepo and Tocumen, Panama, have snout-vent lengths of 39.0 mm. to 46.0 mm. (mean 42.5 mm.). In these specimens, the ratio of the tibia length to the snout-vent length is 0.54 to 0.61 (mean, 0.57); the ratio of the diameter of the tympanum to that of the eye is 0.55 to 0.75 (mean, 0.67). One female has a snout-vent length of 41.0 mm., tibia/snout-vent length ratio of 0.57, and tympanum/eye ratio of 0.76. Two to five (usually three) elongate black spots are present in the scapular region in different individuals. The flanks in some are spotted with brown; in others they are creamy white. A small black spot is present in the groin of some specimens. Usually two to four blotches are present on the anterior and posterior surfaces of the thighs; in some specimens the blotches are reduced to small spots. One or two brown spots are present proximally on the shanks in most specimens. In some individuals tuberculations are scattered on the head and in the tympanic and scapular regions, but the dorsum is smooth in most specimens; the belly is creamy white flecked with brown.

_Cranial Osteology._--The skull of _Hyla foliamorta_ is flat and longer than it is wide. The premaxillary is small and bears 13 to 16 teeth (mean for 2 specimens, 14.8). The alary process of the premaxillary is vertical and concave posteriorly. Ventrally, the premaxillary is completely separated from the prevomer by cartilage. The maxillary is slender; each bears 77 to 84 teeth (mean for 2 specimens, 81). The pars facialis of the maxillary is laterally convex and less than three times the height of the pars dentalis.

The nasal is large and pointed anteriorly and posteriorly in dorsal view. The length of the nasal comprises about 40 per cent of the total length of the skull. The nasals are separated anteromedially by the cartilaginous septum nasi. One protuberance is present on the midlateral concavity of the nasal. Posteriorly, the nasal overlaps the sphenethmoid; posterolaterally the nasal articulates with the palatine. The sphenethmoid is completely ossified and pentagonal in dorsal view. The frontoparietal is elongate, without a pronounced anterior supraorbital process. The frontoparientals are sutured medially throughout their lengths; the frontoparietal fontanelle is absent.

The bony part of the prooetic is narrowly separated dorsolaterally from the squamosal by the cartilaginous crista parotica. The squamosal is large; the anterior arm is pointed. The posterior arm of the squamosal is broad, rounded terminally, and articulates with the prooetic medially.

The prevomer is short and separated anteriorly from the premaxillary and maxillary by cartilage. The posterior margin of the prevomer has a bony articulation with the sphenethmoid. Each prevomer bears five to seven teeth. The palatine is small and edentate. The anterior end of the parasphenoid is narrow (more pointed than in _Hyla boulengeri_). The pterygoid is slender and well developed (Fig. 5A).

_Natural History._--_Hyla foliamorta_ inhabits lowland forests in eastern Panama and breeds in temporary ponds. Males have been observed calling from grasses, bushes, and emergent vegetation near temporary ponds and ditches along roads. William E. Duellman informed me that he found a breeding congregation of this species in June near Chepo, Panama, where males were calling from spiny palms at the edge of a woodland pond. Fouquette (1958) found calling males in May, August, and September near Miraflores Locks, Canal Zone. Calling stations vary from one to two meters above ground. No clasping pairs have been found; only one female is known (KU 101589, from 8 km NE Tocumen, Panama); this gravid individual was collected in early June.

The mating call of _Hyla foliamorta_ consists of one pulsed, low-pitched, moderate trill of about O.5 second duration. Each note is repeated at intervals of 5 seconds to a few minutes. The notes have about 50 pulses per second, a fundamental frequency of 56 cycles per second and a dominant frequency of about 3000 cycles per second (Table 2, Pl. 3B).

Egg deposition sites are unknown. No information is available concerning early development, and little is known about the breeding season of _Hyla foliamorta_. Probably its breeding activities are restricted to the rainy months.

_Tadpoles._--Eight tadpoles were collected from a weedy temporary pond near Chepo, Panama, in early June.

A typical tadpole in stage 35 of development (KU 104244) has a body length of 9.5 mm., tail length of 25.0 mm., and a total length of 34.5 mm. Other characters are as follows: depth of tail equal to length of body; body deeper than wide; distance between eye and nostril equal to distance between eye and spiracle; mouth anteroventral; median part of upper lip bare; rest of lip having one row of papillae; a few other rows of small papillae at corners of mouth; tooth rows 2/3; first upper row entire, second upper row interrupted medially, shorter than first; lower rows shorter than upper rows, third shortest; beak moderately robust; spiracle nearer eye than anus; anal tube short, aperture not extending to border of ventral fin; caudal musculature slender, extending to tip of pointed tail; dorsal fin extending onto body (Table 4).

TABLE 4.--Sizes of Tadpoles of _Hyla foliamorta_ in Relation to Developmental Stages. (Means in parentheses below observed ranges; measurements in mm.)

=======================================================
Stage | N | Body length | Tail length | Total length
--------+---+-------------+-------------+--------------
25 | 2 | 5.0-5.2 | 8.0-8.5 | 13.0-13.7
| | (5.1) | (8.3) | (13.4)
| | | |
26 | 3 | 7.0-7.5 | 12.0-12.4 | 17.0-19.5
| | (7.2) | (12.1) | (18.6)
| | | |
28 | 2 | 6.5-7.0 | 18.0 | 25.0
| | (6.8) | |
| | | |
35 | 1 | 9.5 | 25.0 | 34.5

In life, yellow above, white below; caudal fin greenish yellow with black or gray reticulations; dark line from snout to eye; dark spot behind eye; tail unpigmented except for fine dark reticulations. In preservative body creamy white, transparent below with dark pigment above in some specimens.

_Remarks._--_Hyla foliamorta_ can be confused only with _Hyla boulengeri_. The differences between adults of these species were discussed in _Remarks_ on _H. boulengeri_. The tadpoles of _foliamorta_ have labial papillae on the lower lip and a stripe between the eye and the tip of the snout. By comparison the tadpoles of _boulengeri_ have a bare lower lip and no stripe between the eye and the tip of the snout.

_Distribution._--_Hyla foliamorta_ inhabits the subhumid Pacific lowlands (elevations of less than 100 meters) of Central Panama and Caribbean lowlands of northern Colombia (Fig. 4).

_Specimens Examined._--Panama: _Panama_: 3 km WSW Chepo, KU 77164-9, 101573-5, 104243-4 (tadpoles); 6 km WSW Chepo, KU 77170, 101576-8; 1.5 km SW Naranjal, KU 77171, 77687 (skeleton); 2 km N Tocumen, KU 101579-83, 104349 (skeleton); 8 km NE Tocumen, KU 101584-92.

No specific locality: TNHC 24401.

_Hyla rubra_ Laurenti

_Hyla rubra_ Laurenti, Synopsis Reptilium Emendatum, p. 35, 1768.
Daudin, Hist. Nat. Rainettes Grenouilles Crapauds, II:26, 1802.
Daudin, Hist. Nat. Particuliere Reptiles, 8:53, 1803. Guenther,
Catalogue Batrachia Salientia Brit. Mus., p. 110, 1859. Boulenger,
Catalogue Batrachia Salientia s. Ecaudata, p. 403, February 1,
1882. Dunn, Occas. Papers, Boston Soc. Nat. Hist., 5:413, October
10, 1931.

_Hyla elaeochroa_ (part): Dunn and Emlen, Proc. Acad. Nat. Sci.
Philadelphia, 84:25, March 22, 1932.

_Diagnosis._--Size medium; skull longer than wide; frontoparietal fontanelle absent in adults; snout subovoid; choanae rounded; dorsal stripes present; black vermiculations on posterior surfaces of thighs.

_Description._--Head flat, longer than wide; snout long, subovoid, slightly protruding beyond lower lip; loreal oblique, concave; canthus rounded, indistinct; diameter of eye about equal to interorbital space; tympanum large, about three fifths diameter of eye, smaller than internarial distance; supratympanic fold indistinct; arms short; fingers free of webs; subarticular tubercles distinct; median palmar tubercle large, bifid; inner palmar tubercle on base of first finger flat, elongate; disc of third finger about one half diameter of tympanum; legs moderately long; tarsal fold absent; inner metatarsal tubercle distinct, oval; toes about half webbed; web on fourth toe extending to disc; discs of toes about size of those on fingers; skin smooth above with small granules on head and in scapular region in some specimens; skin on flanks, throat, belly, and lower surfaces of thighs granular; tongue oval, longer than wide, not free behind; choanae small, oval; vocal slits long, lateral to tongue.

In preservative, dorsum pale brown with darker dorsolateral stripes; narrow dark brown line from nostril to eye; groin, anterior surface of thighs, and posteroventral surfaces of shanks creamy tan with dark brown vermiculations; white spots present on thighs in some specimens; throat flecked with brown; belly creamy white or gray.

_Remarks._--The taxonomic history of _Hyla rubra_ Laurenti is confused. Seba (1734:70) illustrated and diagnosed a frog for which he used the name _Ranula, Americana, Rubra_. Linnaeus (1758:213) considered Seba's frog to be a variety of _Hyla arborea_. Laurenti (1768:35) apparently examined the same individual that Seba called _Ranula, Americana, Rubra_. For this specimen, Laurenti used the binominal _Hyla rubra_ and provided a brief diagnosis. The type locality was given as America.

Daudin (1802:26) redescribed the same specimen(s?) treated by Seba and Laurenti and provided a fairly good description and figures. Daudin restricted the type locality to Surinam and indicated that Marin de Baize was the probable collector. Daudin (1802:26 and 1803:53) neglected to consider Laurenti's work, but he applied the same name used by Laurenti. Most authors have credited _Hyla rubra_ to Daudin, but Rivero (1961:120) noted that _Hyla rubra_ Laurenti, 1768, has priority over _Hyla rubra_ Daudin, 1802. Since both Laurenti and Daudin worked on Seba's material, it is reasonable to assume that Daudin redescribed the same frog that was named by Laurenti; this was not an uncommon practice in the early nineteenth century. Thus I conclude that _Hyla rubra_ Daudin, 1802, is a junior synonym of _Hyla rubra_ Laurenti, 1768.

Dunn (1931a:413) first reported _Hyla rubra_ from Central America; he recorded the species from the Canal Zone and San Pablo, Panama. I have examined the material of _Hyla rubra_ from Panama deposited in various museums. Most of the specimens are faded, discolored, and do not have distinct brown vermiculations on the thighs. The specimens seem to be more like _Hyla rubra_ than any of the other species in the _rubra_ group. The presence of oval choanae and a tympanum larger than the largest finger disc separate these specimens from _Hyla elaeochroa_, a species with which _rubra_ has been confused. _Hyla elaeochroa_ does not occur in the Canal Zone or eastern Panama. All museum specimens from Nicaragua, Costa Rica, and western Panama that have been called _Hyla rubra_, plus those mentioned by Dunn and Emlen (1932:25) and Dunn (1933:61) are _Hyla elaeochroa_.

The taxonomic status of the many South American populations referred to _Hyla rubra_ and of other populations now recognized as different species is not clear at the present time. Considerable variation in external characters and in cranial features has been observed in South American _rubra_. A review of the taxonomy of these populations is beyond the scope of this paper. Possibly the Central American specimens herein referred to _rubra_ will ultimately be found to be specifically distinct from those in Surinam. Since I have no osteological material from Central America, I have been unable to describe the cranium in this account. Furthermore, I have no data on the ecology and life history of _rubra_ in Central America.

_Distribution._--_Hyla rubra_ inhabits lowland tropical forests from central-eastern Panama to northern South America and thence through lowlands east of the Andes to northern Argentina (Fig. 6).

_Specimens Examined._--Panama: _Canal Zone_: Gatun, UMMZ 52720 (2); Madden Dam, FMNH 67820; no specific locality, UMMZ 56517 (3), USNM 37863. _Colon_: Cerro Bruja, MCZ 13248. _Darien_: El Real, USNM 140569-70, 140573. _Panama_: Juan Diaz, MCZ 17973; Las Sabanas, MCZ 17581; Rio Trinidad, UMMZ 64003; San Pablo, MCZ 1398-9.

_Hyla elaeochroa_ Cope

_Hyla elaeochroa_ Cope, Jour. Acad. Nat. Sci. Philadelphia, 8:105,
1876 [Holotype.--USNM 30689, Sipurio, Limon Province, Costa Rica;
William M. Gabb collector]. Guenther, Biologia Centrali-Americana,
Reptilia and Batrachia, p. 265, June 1901. Taylor, Univ. Kansas
Sci. Bull., 35:859, July 1, 1952. Duellman, Univ. Kansas Publ.,
Mus. Nat. Hist., 17:270, June 17, 1966.

_Hyla quinquevittata_ Cope, Proc. Amer. Philos. Soc., 23:273,
April 1887 [Holotype.--USNM 14187, Nicaragua; J. F. Bransford
collector]. Guenther, Biologia Centrali-Americana, Reptilia and
Batrachia, p. 268, June 1901. Noble, Bull. Amer. Mus. Nat. Hist.,
38:340, June 1918.

_Hyla rubra_ (part): Dunn and Emlen, Proc. Acad. Nat. Sci.
Philadelphia, 84:25, March 22, 1932.

_Hyla dulcensis_ Taylor, Univ. Kansas Sci. Bull., 39:37, November
18, 1958 [Holotype.--KU 32168, Golfito, Puntarenas Province, Costa
Rica; Edward H. Taylor collector].

_Diagnosis._--Size medium (Male to 38 mm., Female to 40 mm.); skull wider than long; nasals truncate anteriorly; frontoparietal fontanelle moderate in size; snout slightly protruding; tympanum about size of largest discs on fingers; dorsum marked by longitudinal stripes; dark stripe between eye and nostril; in life tan to olive-green with or without dark mark between eyes; bones greenish blue.

_Description._--Head flat, longer than wide; snout long, rounded, protruding beyond mouth; canthus indistinct; length of eye equal to interorbital distance; loreal region not pronounced; tympanum distinct and about two-fifths diameter of eye; interorbital triangle present or absent; arms short; trace of web between fingers, extending as fringe along sides of fingers; first finger very short with small disc; other discs about size of those on toes; discs on third finger and fourth toe as large as tympanum; outer palmar tubercle moderate in size, partly bifid; inner palmar tubercle large, elongate, flat; subarticular tubercles distinct; legs moderately long; tarsal fold absent; inner metatarsal tubercle flat; outer metatarsal tubercle smaller, indistinct; subarticular tubercles moderate in size; fringe on toes to tip of disc of second toe; rest of toes about two-thirds webbed; foot length about two fifths snout-vent length; tibia length about one half snout-vent length; skin above smooth or with minute pustules; belly finely granular; ventral surfaces of thighs and areas below anus granular; skin on ventral surfaces of limbs smooth; tongue relatively large, longer than wide, barely notched behind; vocal slits elongate, lateral to tongue; choanae medium in size. In life, dorsum yellowish brown, olive green, or grayish brown with dark brown spots on snout, dark brown stripe from nostril to eye, dark yellow-brown interorbital triangle, and dark supratympanic region; generally five interrupted longitudinal dark brown stripes on dorsum (one on each flank, pair of paravertebral and one vertebral); flanks pale yellow; groin yellowish brown; thighs marked with one or two transverse yellow-brown blotches; shanks with two or three yellow-brown blotches above; spaces between blotches on thighs, shanks, tarsi, and feet yellow; brown spots on tarsi and in some specimens on feet; arm pale yellow with pale brown spots; belly creamy white having slight blue-green tint; vocal sac and chin yellow; axillary region yellow, blue-green in some specimens (Pl. 2A).

In preservative, head and dorsum yellowish brown; dark brown stripe from nostril to eye; dark brown spots on snout; a dark brown interorbital triangle with apex directed backward; dark brown supratympanic region; dorsal stripes same as in living individuals; flanks pale yellow with brown spots in some specimens; groin creamy white; thighs and shanks having or lacking transverse dark brown blotches; spaces between blotches creamy white or yellow-brown; arms pale yellowish brown; belly and vocal sac creamy white.

_Variation._--Geographic variation in size and some proportions, such as the ratio of tibia length to snout-vent length and the ratio of the diameter of the tympanum to that of the eye, have been observed in this species. The largest individuals are from the Golfo Dulce region (samples from Piedras Blancas and Rincon de Osa), Puntarenas Province, Costa Rica. The smallest individuals are from El Recreo, Zelaya Province, Nicaragua, and from the Caribbean lowlands of Costa Rica.

The diameter of the tympanum is proportionately larger (relative to the size of the eye) in males from Tilaran, Guanacaste Province; the tympanum is nearly as large in males from Piedras Blancas, Puntarenas Province, and Puerto Viejo, Heredia Province, Costa Rica. The lowest ratios occur in individuals from Almirante, Bocas del Toro, Panama, in specimens from the Caribbean lowlands of Costa Rica (except Puerto Viejo), and in those from El Recreo, Zelaya Province, Nicaragua. In general, the tympanum is proportionately larger in females than in males; the tympanum is largest in females from the Pacific lowlands of Costa Rica (Table 5).

Color variation has been observed in individuals from the same population, as well as in individuals from different localities, between males and females, and from night to day. In life, most individuals from the Pacific lowlands of Costa Rica are dark tan to greenish gray above with dark brown longitudinal stripes that are entire or broken, but some specimens (mostly males) are dusky brown and lack longitudinal stripes or an interorbital triangle; females usually have the dark interorbital triangle and the stripes on the dorsum. Individuals from Turrialba, Cartago Province, Costa Rica, are pale olive-tan with olive-brown markings. Individuals from Puerto Viejo, Heredia Province, Costa Rica, are uniformly yellowish brown with or without dark longitudinal stripes. Specimens from El Recreo, Zelaya Province, Nicaragua, are like those from Puerto Viejo. Males from Almirante, Bocas del Toro, Panama, are pale brown with dark brown longitudinal stripes and an indistinct interorbital triangle. Females have a distinct interorbital triangle and dark brown blotches on the thighs and shanks.

By night, the dorsum usually is pale yellow, and the belly is creamy white. By day, the dorsum is dark tan; the stripes and spots are darker, and the belly is yellowish white. Taylor (1952) noticed that considerable variation in color pattern occurred from night to day in individuals from Turrialba, Cartago Province, Costa Rica. At night some individuals lacked a dorsal pattern, but by day many of these individuals developed dorsal stripes.

_Cranial Osteology._--The skull of _Hyla elaeochroa_ is slightly wider than it is long, and flat. The premaxillary is small and bears 10 to 15 teeth (mean for 9 specimens, 12.3). The alary process of the premaxillary is small, vertical, and slightly concave posteriorly. Ventrally, the premaxillary is partially united to the prevomer by ossification. The maxillary is slender and bears 70 to 82 teeth (mean for 9 specimens, 74.3). The pars facialis of the maxillary is laterally convex and is about twice as high as the pars dentalis.

The nasal is large, robust, anteriorly truncate, but pointed posteriorly in dorsal view. The nasal comprises about 45 per cent of the total length of the skull. There is an anterior cartilaginous septum nasi separating the two nasals; the latter overlap the sphenethmoid posteriorly. Each nasal bears a shallow concavity in the midlateral side and lacks a maxillary process. Dorsally, the sphenethmoid is wider than long, roughly pentagonal in shape; the frontoparietal is elongate, smooth, and bears a small anterior supraorbital process. The sphenethmoid and frontoparietal form the anterior margin of the frontoparietal fontanelle; the fontanelle is narrow anteriorly and wider posteriorly (Fig. 5B).

The entire distal surface of the prooetic is in contact with the posterior arm of the squamosal. A narrow cartilaginous crista parotica is visible dorsally in some specimens. The squamosal is broad posteriorly but its anterior arm is slender and not in contact with the maxillary.

TABLE 5.--Geographic Variation in Size and Proportions in Males of _Hyla elaeochroa_. (Means in parentheses below observed ranges.)

==========================================================================
| |Snout-vent| Tibia | |
| | length | length/ |Tympanum/|Foot length/
Locality | N | (mm.) | snout-vent | eye | snout-vent
---------------------+----+----------+------------+---------+-------------
Nicaragua: El Recreo | 9 | 28.0-30.3| 0.51-0.57 |0.47-0.59| 0.39-0.54
| | (29.3) | (0.55) | (0.51) | (0.41)
| | | | |
Costa Rica: Tilaran | 21 | 28.8-33.6| 0.47-0.57 |0.48-0.65| 0.40-0.46
| | (30.6) | (0.52) | (0.59) | (0.41)
| | | | |
Costa Rica: Puerto | 22 | 26.3-32.4| 0.49-0.54 |0.48-0.65| 0.38-0.45
Viejo | | (29.7) | (0.52) | (0.57) | (0.42)
| | | | |
Costa Rica: Turrialba| 95 | 28.1-35.0| 0.47-0.56 |0.47-0.68| 0.37-0.46
| | (30.6) | (0.51) | (0.56) | (0.41)
| | | | |
Costa Rica: Bataan, | 26 | 26.3-32.7| 0.47-0.54 |0.45-0.66| 0.36-0.44
Limon, and Suretka | | (30.0) | (0.51) | (0.50) | (0.41)
| | | | |
Costa Rica: Piedras | 21 | 33.3-37.7| 0.50-0.54 |0.48-0.64| 0.40-0.46
Blancas | | (35.2) | (0.51) | (0.57) | (0.43)
| | | | |
Costa Rica: Rincon de| 24 | 31.4-35.9| 0.50-0.56 |0.45-0.61| 0.40-0.46
Osa | | (34.1) | (0.53) | (0.54) | (0.43)
| | | | |
Panama: Bocas del | 6 | 31.0-33.5| 0.49-0.54 |0.47-0.50| 0.41-0.43
Toro | | (32.1) | (0.51) | (0.48) | (0.42)

Living _Hyla_: (A) _H. boulengeri_ (KU 86322) and (B) _H.
foliamorta_ (KU 101576), x 2.]

Living _Hyla:_ (A) _H. elaeochroa_ (KU 91688), (B) _H. staufferi
staufferi_ (KU 57791), and (C) _H. staufferi altae_ (KU 101688), x
2.]

Audiospectrograms and sections of mating calls of (A) _Hyla
boulengeri_ (KU Tape No. 511) and (B) _H. foliamorta_ (KU Tape No.
511) and (B) _H. foliamorta_ (KU Tape No. 288).]

Audiospectrograms and sections of mating calls of (A) _Hyla
elaeochroa_ (KU Tape No. 97), (B) _H. s. staufferi_ (KU Tape No.
93), and (C) _H. staufferi altae_ (KU Tape No. 502).]

The prevomer is short, and broadest anteriorly. The prevomer is joined to the premaxillary by ossification. The posterior margin of the prevomer bears a narrow cartilaginous articulation with the sphenethmoid. The anterolateral and posterolateral processes of the prevomer form an incomplete bony margin to the small choanae; each prevomer bears four to seven teeth. The palatine is small, curved anteriorly and edentate. The anterior part of the parasphenoid is robust and ends in a point. The pterygoid is slender and weakly developed.

_Natural History._--_Hyla elaeochroa_ inhabits humid lowland tropical forests in lower Central America and breeds in temporary ponds. Clasping pairs, gravid females, and calling males have been found mostly in June, July, and August. William E. Duellman informed me that he also found males calling in mid-February, late April, and May. Duellman (1967) reported detailed observations of the social organization in the mating call of _Hyla elaeochroa_. The choruses in this species are initially organized, but when many individuals call, the chorus loses organization. I observed this species breeding in a temporary pond at Puerto Viejo, Heredia Province, Cost Rica, in late June. Calling males and clasping pairs were extremely abundant within a few hours after a heavy rain. Males were mostly found calling from low emergent herbs in the pond and less commonly from bushes and trees to heights of six meters above the water. Calling males were also observed at Ricon de Osa, Puntarenas Province, Costa Rica, in late July. These breeding individuals were found in a shallow pond at the edge of a wet forest. Calling stations were less than two meters in height. John D. Lynch informed me that after a heavy rain in early August, he found several hundred individuals congregated in a small grassy pond less than a foot deep, at Rincon de Osa. Males were calling from sites on grass stems a few centimeters above the water.